Partway to Cleaner Coal

Researchers seeking to make coal a more environmentally friendly fuel have long believed that requiring new coal-burning power plants to capture all their carbon dioxide emissions is the cheapest way to keep the greenhouse gas out of the atmosphere. But full-capture requirements may prove counterproductive in the short term because they create such big hurdles for power producers: although no state yet requires full capture, the costs of complying with such a policy would be prohibitive. “No one is really able to [achieve full capture] right now because of the technological and economic risks associated with it,” says ­Ashleigh ­Hildebrand, a graduate student in chemical engineering and the Tech­nology and Policy Program at MIT.

Working with Howard J. Herzog, principal research engineer with the MIT Energy Initiative, Hildebrand created a model to study what would happen if, as an intermediate step, power producers adopted technologies that could capture just some of their carbon dioxide emissions. “We started thinking about the idea of backing off on the capture requirements, and thinking, What does it mean if you achieve different levels of capture–if you achieve 10 percent versus 50 percent versus 90 percent?” ­Hildebrand says. The model revealed that partial capture may be more worthwhile than previously thought. “By reducing the capture requirement, we’re essentially reducing the cost and the risk associated with it,” says ­Hildebrand. As a result, power producers may be able to implement partial carbon dioxide capture more quickly than they could full capture; widespread voluntary adoption of full-­capture policies is anticipated to take 10 to 15 years. “If we can get partial capture implemented sooner in more plants, we can actually generate more knowledge from it, which will act to expedite large-scale deployment of full capture,” says Hildebrand. “And that’s the long-term goal.”